1. Field of the Invention
The present invention relates to a field emission display (FED) device, and more particularly to an FED device using nano-scale electron emitters having low emitting voltage and excellent mechanical properties.
2. Description of Related Art
In a conventional FED device, electrons are extracted from emitters on a cathode by applying an emitting voltage to tips of the emitters. The emitters are made of metals such as molybdenum, or semiconductive materials such as silicon. The electrons impinge on phosphors on the back of a transparent cover plate and thereby produce an image.
One major problem of the conventional FED device is that the work functions of metals or semiconductive materials used for the emitters are large. That is, the emitting voltage required for electron emission is very high. Another major problem is the poor mechanical properties of the emitters. When residual gas particles in a vacuum within the FED device collide with electrons, the gas particles become ionized. The emitters are bombarded with these gas ions, and some of the emitters are degraded to the point where they can no longer function as an electron emission source. These problems reduce the performance and lifetime of the emitters. To overcome these problems, a new kind of emitter having a low work function and excellent mechanical properties is needed for an FED device to provide better performance and longer lifetime.
Moreover, in a typical FED device, most of electrons are extracted from the emitters, but there are still a certain amount of electrons extracted from the outermost layer of the cathode when an electrical field is applied. The electrons extracted from the outermost layer of the cathode cause non-uniform electron emission, and therefore non-uniform brightness at the phosphors. To overcome this problem, new means are needed for the FED device to achieve uniform electron emission.
In view of the above-described problems of the related art, an object of the present invention is to provide a field emission display (FED) device with nano-scale electron emitters having low emitting voltage and excellent mechanical properties.
Another object of the present invention is to provide an FED device which has accurate and reliable electron emission.
In order to achieve the objects set above, an FED device in accordance with a preferred embodiment of the present invention comprises a cathode plate, a resistive buffer in contact with the cathode plate, a plurality of electron emitters formed on the resistive buffer, and an anode plate spaced from the electron emitters thereby defining an interspace region therebetween. Each of the electron emitters comprise a nano-rod first part formed on the buffer, and a conical second part formed on a free end of respective nano-rod. The buffer and the nano-rods are made from silicon carbide; namely (SiCX), in which x can be controlled according to the required stoichiometry. The combined buffer and nano-rods has a gradient distribution of electrical resistivity such that highest electrical resistivity is nearest the cathode plate and lowest electrical resistivity is nearest the anode plate. The conical parts are made from molybdenum. When emitting voltage is applied between the cathode and anode plates, electrons emitted from the electron emitters traverse the interspace region and are received by the anode plate. Because of the gradient distribution of electrical resistivity, only a very low emitting voltage is needed.
In an alternative embodiment the combined buffer and nano-rods can incorporate more than one gradient distribution of electrical resistivity.
Other objects, advantages and novel features of the present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawing, in which: